Birmingham: Visiting a black church bombed by the Ku Klux Klan during the civil rights era, Democratic presidential candidate Joe Biden has framed current racial tensions as part of an enduring struggle that is older than the nation.

"In a centuries long campaign of violence, fear, trauma, brought upon black people in this country, the domestic terrorism of white supremacy has been the antagonist of our highest ideals since before the founding of this country," Biden told the 16th Street Baptist Church congregation in downtown Birmingham as they commemorated the 56th anniversary of the bombing that killed four black girls in 1963.

"It's in the wake of these before-and-after moments," Biden added, "when the choice between good and evil is starkest." Biden's appearance comes at an inflection point for Democrats' 2020 leader in the polls.

He is trying to capitalize on his strength among older black voters while navigating criticism from some African American and other nonwhite leaders, particularly younger ones, who take a skeptical view of the 76-year-old white man's willingness and ability to address systemic racism.

During his 20 minutes at the pulpit, Biden condemned institutional racism as the direct legacy of slavery and lamented that the nation has "never lived up to" the ideals of equality written into its founding documents.

But then he added a more personal note perhaps the closest he would come to addressing his detractors. "Those who are white try," Biden said, "but we can never fully understand."

The former vice president called out the names of the bombing victims Addie Mae Collins, Denise McNair, Carole Robertson and Cynthia Wesley and he drew nods of affirmation as he warned that "the same poisonous ideology that lit the fuse on 16th Street" has yielded more recent tragedies, including in 2015 at a black church in South Carolina, in 2018 at a Jewish synagogue in Pittsburgh and in August at an El Paso, Texas , Wal-Mart frequented by Latino immigrants.

The Birmingham church, Biden said, offers an example to those communities and a nation he said must recommit itself to "giving hate no safe harbor demonizing no one, not the poor, the powerless, the immigrant or the 'other.'"

From his long time in government, first as a senator and then vice president to Barack Obama, the first black president, Biden has deep ties in the black community. Though Biden didn't mention President Donald Trump in his remarks, he has made withering critiques of the president's rhetoric and policies on race and immigration a central feature of his candidacy.

Yet Biden sometimes draws searing appraisals from younger nonwhite activists who point to complexities in his record.

That includes his references to working productively alongside segregationist senators in the 1970s to distrust over his lead role in a 1994 crime law that critics frame as partially responsible for mass incarceration, especially black men.

The dynamics flared up again Thursday after Biden, during a Democratic debate, offered a sometimes incoherent answer when asked how the nation should confront the legacy of slavery. At one point, Biden suggested nonwhite parents use a play a record player to help their children with verbal and cognitive development.